Some golfers have difficulty imparting a desired trajectory to a golf ball during play. For example, many golfers have club swings that tend to slice, or push, the ball. Slice, push, draw, hook, and pull are common terms in the game of golf and describe trajectories as projected on a ground plane. A “slice” refers to a trajectory that curves toward a direction a golfer faces when addressing the ball. A “push” refers to a trajectory that is substantially straight, but off-center in a direction the golfer faces at address position. A “hook” refers to a trajectory that curves in a direction opposite a slice. A “pull” refers to a trajectory that is substantially straight but travels off-center in a direction opposite a push. A “draw” typically refers to a trajectory that curves mildly, that is to say less severely, in the direction of a hook. A “fade” typically refers to a trajectory that curves mildly in the direction of a slice.
Club head motion throughout a golf swing, and thus ball trajectory, results at least in part from movement of many linkages formed by a golfer's body. Each linkage has one to six degrees-of-freedom. Many factors can influence the extent to which motion at the linkages occur, including without limitation golfer strength, flexibility, swing technique, swing speed, rhythm, club characteristics, ground surface, and the like. Many golfers are frustrated in their attempt to manipulate these various factors to achieve a desired club head motion and ball trajectory. Hence, club manufacturers constantly strive to improve club characteristics to mitigate swing deficiencies and otherwise help the golfer achieve the desired trajectory.
Traditional golf clubs include a shaft, grip and a club head. The club head receives the shaft in a hosel region such that the center of mass of the club head has some eccentricity relative to the shaft centerline axis when the club head is at normal address position. During a swing, mass distribution of the club can cause the club head to tend toward a particular motion throughout the golfer's swing. For example, a golf club with heel biased weighting tends to cause a club head motion that imparts a draw to the ball.
Several attempts have been made to achieve heel biased weighting. For example, during assembly of the club head to the shaft, weights have been applied to one or both of the hosel and shaft. In some instances, weights have been applied externally, that is to say in a region visible when the golfer addresses the ball. For example, alloys of copper, lead, tungsten, and the like have been adhered to club heads at various locations to manipulate mass distribution, giving the club head, for example, a heel-biased or toe-biased weighting.
Although a manufacturer can manipulate club head mass distribution, overall sensory perception of the club remains important to many golfers. For example, some golfers are accustomed to a particular look and feel of a golf club when addressing a ball. Significant deviation in club appearance from the “norm” can distract a golfer prior to and during her swing, possibly causing an undesirable ball trajectory or result. Prior golf clubs with biased weighting, heel-biased or otherwise, generally have deviated significantly from the conventional appearance of an iron when viewed from the golfer's perspective at address position. Accordingly, prior golf clubs that have provided biased weighting generally have not been well received.